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CRaTER Pre-Environmental Review (I-PER) Environmental Test Planing Bob Goeke

CRaTER Pre-Environmental Review (I-PER) Environmental Test Planing Bob Goeke. September 10-11, 2007. Test Timelines. Serial Number 2 Serial Number 1 Science Calibration MGH September 15 October 13 Vibration Draper Labs September 24-25 October 29-30 Thermal-Vacuum

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CRaTER Pre-Environmental Review (I-PER) Environmental Test Planing Bob Goeke

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  1. CRaTER Pre-Environmental Review(I-PER)Environmental Test PlaningBob Goeke September 10-11, 2007

  2. Test Timelines Serial Number 2Serial Number 1 • Science Calibration • MGH September 15October 13 • Vibration • Draper Labs September 24-25October 29-30 • Thermal-Vacuum • MIT September 26-October 10October 31-November 14 • EMC/EMI • Chomerics October 15-26(not required) • Science Calibration • MGH December 8December 15 The MGH dates are fixed by facility availability; it was the best we could negotiate. The remaining facility dates are, within reason, flexible.

  3. Functional Test Procedures • Short Form Functional • Tests all primary functionality including command and telemetry packet handling. • All active electronics except redundant 1553 chain exercised by internal cal sources. • Verifies 1Hz clock and time message handling. • Verifies detector bias, detector leakage currents, detector noise levels. • Long Form Functional • Tests every command bit and every telemetry data item. The only function not tested to completion is the Discriminator Mask (an exhaustive test would take >1012 years) though each bit in the mask is separately checked (a 3-1/2 hour process). • Redundant 1553 bus is verified. • Instrument response to loss of 1Hz clock is verified. • Power Bus variation (27->35VDC) is tested. • Internal RAM pattern and FPGA internal logic test is performed. • Thick (D2, D4, D6) detector aliveness is verified by use of gamma rays from a 60Co source; the thin (D1, D3, D5) detectors are not responsive to available laboratory sources.

  4. 60Co Thick Detector Response

  5. 60Co Thin Detector Response

  6. Trend Monitoring • Environmental Testing and at I&T • Input Power • Internal regulated voltages • Detector bias voltages and individual bias currents • But bias currents double every 7C • Internal temperatures • Monitor deltas between various points and reference temperature • Singles rates • Includes background events ... • Measurement chain noise • Requires data analysis of primary science stream while injecting internal cal signal • Need to reject natural background to get good statistics • On-orbit cosiderations • Internal calibration signal noise measurements might interfere with science data collection; would probably only be done as a troubleshooting diagnostic.

  7. Mechanical Work Since CDR • A low level sine survey was performed in June 2006. • The results of this test were used to update the SolidWorks model. • An FEA was then performed on the CRaTER Design. The results revealed the following responses; • The Analog Board experienced a peak response of ~130 g^2/Hz @ 519 Hz. • The Digital Board experience a peak response of ~400 g^2/Hz. • Top Cover experienced a peak response of ~140 g^2/Hz. • Bottom Cover experienced a peak response of 190 g^2/Hz. • The E-Box experienced a peak response of 20.3 g^2/Hz @ 520 Hz.

  8. Mechanical Work Since CDR • CRaTER Mechanical Mockup Random Vibration Test, Oct 2006 • The Mechanical Mock up consisted of the Engineering Telescope, the Engineering E-Box Housing, the engineering top and bottom covers, and G10 blanks for the Analog Board and Digital Board. Mass was added to the Analog and Digital G10 blank boards. Aluminum blanks were also installed to reflect the two DC/DC converters and the EMI filter. • Two triax Accelerometers were placed on the Telescope. One Triax accelerometer was placed on the E-box housing. • Single axis accelerometers were placed on the Analog board, Digital board and the top cover. • The tests performed were a Pre and a Post ½ g sine sweep, the Random Vibration, and the Sine Vibration Environment on each axis at prototype levels and durations.

  9. Mechanical Work Since CDR • Results of the Random Vibration test on the CRaTER Mock up Unit. • Z Axis (Normal to mounting surface) • Dominant Frequency at ~975 Hz, w/ peak response of ~20 g^2/Hz. • Analog Board ~720 Hz, with a peak response of 7 G^2/Hz. • Digital Board ~410 Hz, with a peak response of ~400 g^2/Hz. • Top Cover ~415 Hz, w/ a peak response of ~600 g^2/Hz • X Axis (lateral) • First frequency at ~ 975 Hz • Y Axis (lateral) • First frequency at ~ 1200 Hz • The frequencies matched very closely to the Solidworks Model and the FEA Model • First frequency at 435Hz (top cover), • First Frequency of the system at 1158 Hz. • Analog Board- 648 Hz • Digital Board- 497 Hz • Top Cover- 435 Hz.

  10. Post Random Vibration Test • The Telescope passed functional testing after the Vibration Test. The Telescope was then disassembled to inspect the six Detectors and the Detector PWA. There were no visible signs of damage to the external or internal pieces, the detectors or the PWA. The unit was reassembled and is passed functional testing again. • The mockup digital and analog boards were also inspected visually and showed no signs of crazing around the thru holes. • There were no visible signs of damage or loosened components on the E-box.

  11. Response Comparisons • The responses from the Random Vibration and the FEA had mixed correlations. * There was not an accelerometer on the bottom cover for comparison.

  12. Discussion on FEA vs Random Vibration Test • The top cover displayed the largest response to the vibration test. As a result the top cover was redesigned to increase the stiffness. • First frequency is 844 Hz. • Mass =.8 lbs • With 600 g load the max stress is 6.4 e^6 N/M^2. • MOS = 48

  13. Discussion on FEA vs Random Vibration Test • The FEA Model was not tweaked after the vibration testing. It was deemed unnecessary at the time. • The analysis shows that the Margins of Safety are met using the Random Vibration response values. • RFA- LRO-CRaTER-PDR was written to recommend that an integrated FEA be performed. This action was competed and closed in March of 2007.

  14. Flight Vibration Test Approach • The first unit will be tested to proto flight levels and durations. • Sine Burst testing will be performed on the first Flight Unit only, S/N 002. • The second unit is qualified by similarity. • The second unit will be tested to acceptance levels and durations. • There is no notching or force limiting necessary.

  15. Flight Vibration Test Setup Preparation • Crater will be bagged in clean ESD safe material for ESD and contamination control. • The environmental test facility meets our ESD requirements. • CRaTER will not require Nitrogen purging during vibration testing. There will be a Nitrogen purge prior to and post vibration functional testing. • The Thermal Blanket will not be installed for the Vibration Testing.

  16. Vibration Test Setup-Shaker Interface • There will be two single axis control accelerometers mounted to the interface fixture, diametrically opposite each other. • The interface plate is an eight sided 2” thick aluminum plate that will be secured to the shaker with ~twelve (12) 1” diameter high strength bolts.

  17. Vibration Test Setup-Crater • There will be two tri-axis accelerometers used for Vibration testing. One will be on the Telescope Assembly and the second will be on the Electronics-Box Assembly.

  18. Vibration Testing • Procedure: 32-06004.03 • All environments obtained from the LRO Mechanical Systems Spec, 431-SPEC-000012, rev D. • Test Flow, First Flight Unit • Long Form Functional Test Prior to starting the Vibration test. • First Axis (preferably Z) • ¼ g Low-Level Resonance Search (5-2000 Hz, 2 Oct/Min) • Sine Vibration Environment (5 - 50 Hz, 4 Oct/Min) • Structural Loads (Sine burst, 10g at 35 Hz) • Random Vibration (14.1 grms) • ¼ g Low-Level Resonance Search (5-2000 Hz, 2 Oct/Min) • Short Form Functional Test • Repeat for additional two axes • After all three axis a Long Form Functional Test will be performed. • Pyro-shock deferred to orbiter level

  19. Pre and Post Vibe Sine sweep • A pre and a post vibration ¼ g sine sweep will be performed on each axis. The test will be performed at a rate of 2 octaves per minute.

  20. Sine Vibration Environment The first Flight Unit will be tested to Protoflight levels and the second Flight Unit will be tested to acceptance levels – both with a sweep rate of 4 oct/minute.

  21. Structural Load Testing • Strength Test-Sine Burst • Five cycles at 35 Hz. The level is 10 g’s (Limit load x 1.25) • The natural frequency of CRaTER is 975 Hz • Thus the response of the CRaTER instrument is well within the static region of its response curve • Test performed only on the first Flight Unit. The second Flight Unit is qualified by similarity

  22. Random Vibration Environment • The first Flight Unit will be tested to Protoflight levels. • The second Flight Unit will be tested to the Acceptance Levels.

  23. Pass/Fail Criteria • Acceptance Criteria for CRaTER • Complete testing to limit levels with the appropriate test factor. • No structural degradation after test. • No unexplained frequency shifts more than 5% between pre and post test. • No Visible damage that is a result of the test environment. • Pass all functional performance testing performed during and upon completion of the test.

  24. Thermal Design Overview • CRaTER instrument is simple from thermal point of view • Thermally coupled to LRO spacecraft • No operational heaters • No survival heaters • No radiators • No gradient requirements • CRaTER dissipates 6.7 Watts of heat • 6.51 watts in electronics box • 0.16 watts in telescope assembly • CRaTER instrument is completely covered with thermal blankets • 15 layer MLI over majority of instrument • 1 layer of Kapton over telescope apertures (35 mm nominal aperture) • There have been no thermal design changes since CDR

  25. CRaTER T-Vac Setup • Vacuum Chamber is a 2’x2’x2’ stainless steel chamber • Interface plate to drive the spacecraft interface temperatures • TQCM in chamber to monitor bakeout • Cobalt 60 source for use during long form functional tests • Power source and spacecraft simulator feed through in chamber

  26. Thermal-Vacuum Testing • Procedure: 32-06005.01 • Test Flow • Initial Long Form Functional at 0C • Hot Survival at +50C • Thermal Balance at +25C and -30C (on serial number 1 only) • Hot Turn On & Long Form Functional at +40C • Cold Turn On & Long Form Functional at -40C • Seven cycles of +40C/-40C with Short Form Functionals • Final Long Form Functional at 0C • TQCM measurement at +35C • Bakeout certification performed at GSFC

  27. Thermal-Vacuum Timeline

  28. Test Tolerances and Temperature Locations • Test tolerances +/- 2 degrees C • Thermal slews commanded at 0.5 deg C/minute • Temperature Monitor locations • Spacecraft provided PRT on inner wall between electronics enclosure and telescope assembly (this is the instrument “reference” temperature) • AD590 on telescope pre-amp board • AD590 on analog board • AD590 on 1553 transceiver • AD590 on power converter • AD590 on inner wall (next to PRT) • 2 PRTs on interface plate • Success criteria: no statistically significant shift in Long Form Functional results

  29. Thermal Modeling • Several deficiencies recently found in the model required that the CRaTER model be re-built from scratch • This has delayed the pre-test analysis for thermal balance testing • LRO Project and CRaTER have agreed to delay performance on thermal balance test until SN 1 is tested in early November • This will allow enough time to perform pretest analysis, submit the results to GSFC, and agree on the appropriate thermal balance test setup • Note that all thermal cycling tests are being performed to (qualification) limits specified in the Thermal ICD • The CRaTER (validated) thermal model is an input to the overall Observatory thermal model • The results of the Observatory model are required to predict the nominal on-orbit operating conditions of the instrument • The ICD test limits were chosen using engineering judgment to envelope the range of possible answers coming out of the Observatory model.

  30. CRaTER Contamination Requirements • CRaTER self-imposed contamination requirements • The only internal contamination sensitive items are the detectors, and they have been shown to be quite insensitive. Buildup of passive contamination does not effect quantum efficiency. • The engineering unit has been exposed to a laboratory atmosphere for over a year and not suffered for it. • We have requested periodic GN2 purges as a precaution, especially in the launch site environment. • Although CRaTER is not contamination sensitive, basic precautions have been taken to remain compatible with other experiments • Selection of low outgassing materials • Appropriate fabrication, assembly and handling procedures • Spacecraft imposed contamination requirements (from LRO Contamination Control Plan, 431-PLAN-000110) • External cleanliness at delivery: 450 A/2 • Outgassing requirement: <5.0E-11 g/cm^2/sec

  31. CRaTER Contamination Control • Control methods • CRaTER will be bagged when not residing in a clean bench (e.g.: during science calibration runs, vibration testing, EMC) • Periodic GN2 purge • Outgassing • Primary bakeout of CRaTER instrument to occur during T-VAC testing at MIT • External cleanliness verified at MIT prior to delivery • Bake out certification baselined to occur at GSFC. However, there will be a TQCM in T-VAC chamber at MIT and it may be possible to certify CRaTER at MIT

  32. EMC/EMI Testing • Procedure: 32-06006.01 • Test Flow • Long Form Functional (at MIT) • CE01 -- monitor primary science & housekeeping • CE02 -- monitor primary science & housekeeping • RE02 -- monitor primary science & housekeeping • CS01 -- normal mode with internal cal • CS02 -- normal mode with internal cal • CS06 -- normal mode with internal cal • RS03 -- normal mode with internal cal • Long Form Functional (at MIT)

  33. Instrument Modes for EMC • Emissions • Instrument has only one operating mode, so choices are limited • Traffic on the external data bus is independent of instrument data processing rate • Turn internal cal on to high rate (2KHz) to simulate worst case internal processing • Susceptibility • For CW injection use internal cal signal to monitor measurement chain noise • For transient susceptibility monitor detector singles rates

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